During the construction of buildings, parking structures, and the like, concrete is often the material of choice for floors, walls, supporting structures, and other building components. It is recognized that substantial voids may be specifically placed within the poured concrete structures to minimize the volume of concrete introduced into the structure and hence minimize the resulting cost, but without substantially affecting the strength of that resulting structure. It is common, for instance, to pour a concrete floor over a number of boxes so as to form an egg-crate shape on the bottom side of the structure. The region between the recesses may be considered as concrete beams.
Formation of such recesses in concrete structures is typically through the use of wood or metal forms. Obviously, such forms are often difficult or impossible to remove from the underside of a concrete structure. Moreover, the presence of those unremoved forms may add significant weight and corrodible (or termite-infestable) components to the structure. Some have proposed the use of paper forms to produce voids in concrete structures.
U.S. Pat. No. 2,823,442, to Miller et al., teaches the use of a carton form suitable for the production of recesses or voids in concrete wall or floor structures. The form is in the shape of a longitudinal tray constructed of folded corrugate sheets. The tray is supported in a rigid fashion by a filler structure also formed of corrugate. The filler is produced by folding a corrugate strip into a zig-zag series of folds so to form rectangles. The ends of the folded rectangles are stapled to the interior sides of the trays to form webs within the resulting rigid box. The corrugate may be waterproofed or lubricated so, respectively, to provide additional structural strength during the pouring step or to allow removal of the form after the curing step.
U.S. Pat. No. 3,512,747, to Stark, describes a form used in producing an elongated void in a poured concrete structure. The corrugate form is made by assembling a pair (or more) of mirror-image sheets by folding them in such a way to form either a square cross-section or octagonal cross-section sleeve. The edges of the outer sheets are formed into corrugate inner structures, or pads, which form ribs within the resulting sleeve.
U.S. Pat. No. 3,381,929, to Bancher, teaches a flat concrete construction form assembly produced using, preferably, a paper honeycomb core, fiberboard outer cover, and a lightweight metal framework holding the core and center coverings together. The spacing between a pair of these construction-form assemblies may be adjusted by use of a cooperating set of clips (which fit into grooves found in the lightweight metal framework) and some large U-shaped clips which space the set of form assemblies apart at a particular distance.
U.S. Pat. No. 5,098,059, to Sawyer, describes a concrete forming member produced from a core of polystyrene or polyurethane and preferably having a flexible, non-permeable plastic film appended to the core. The impermeable face may be contoured to define a decorative pattern, such as an artificial brick facing, or the cast concrete. In some variations of the invention, a structural element is appended to the remote side of the plastic forming member to allow support of the structure during concrete pouring.
None of the cited references show the use of concrete forms produced primarily of paper honeycomb, which forms are self-supporting, and which are physically able to support workers during the pouring step.